The present invention relates to copper (Cu) and/or Cu alloy metallization in semiconductor devices, and to a method for manufacturing semiconductor devices with reliable, low resistance Cu or Cu alloy interconnects. The present invention is particularly applicable to manufacturing high speed integrated circuits having submicron design features and high conductivity interconnect structures.
The escalating demand for high density and performance impose severe requirements on semiconductor fabrication technology, particularly interconnection technology in terms of providing reliable low Rxc3x97C (resistancexc3x97capacitance) interconnect patterns with higher electromigration resistance, wherein submicron vias, contacts and trenches have high aspect ratios.
Conventional semiconductor devices comprise a semiconductor substrate, typically doped monocrystalline silicon, and a plurality of sequentially formed interlayer dielectrics and conductive patterns. An integrated circuit is formed containing a plurality of conductive patterns comprising conductive lines separated by interwiring spacings, and a plurality of interconnect lines, such as bus lines, bit lines, word lines and logic interconnect lines. Typically, the conductive patterns on different layers, i.e., upper and lower layers, are electrically connected by a conductive plug filling a via hole, while a conductive plug filling a contact hole establishes electrical contact with an active region on a semiconductor substrate, such as a source/drain region. Conductive lines are formed in trenches which typically extend substantially horizontal with respect to the semiconductor substrate. Semiconductor xe2x80x9cchipsxe2x80x9d comprising five or more levels of metallization are becoming more prevalent as device geometry""s shrink to submicron levels.
A conductive plug filling a via hole is typically formed by depositing an interlayer dielectric on a conductive layer comprising at least one conductive pattern, forming an opening through the interlayer dielectric by conventional photolithographic and etching techniques, and filling the opening with a conductive material, such as tungsten (W). Excess conductive material on the surface of the interlayer dielectric is typically removed by chemical mechanical polishing (CMP). One such method is known as damascene and basically involves forming an opening in the interlayer dielectric and filling the opening with a metal. Dual damascene techniques involve forming an opening comprising a lower contact or via hole section in communication with an upper trench section, which opening is filled with a conductive material, typically a metal, to simultaneously form a conductive plug in electrical contact with a conductive line.
High performance microprocessor applications require rapid speed of semiconductor circuitry. The control speed of semiconductor circuitry varies inversely with the resistance and capacitance of the interconnection pattern. As integrated circuits become more complex and feature sizes and spacings become smaller, the integrated circuit speed becomes less dependent upon the transistor itself and more dependent upon the interconnection pattern. Miniaturization demands long interconnects having small contacts and small cross-sections. As the length of metal interconnects increases and cross-sectional areas and distances between interconnects decrease, the Rxc3x97C delay caused by the interconnect wiring increases. If the interconnection node is routed over a considerable distance, e.g., hundreds of microns or more as in submicron technologies, the interconnection capacitance limits the circuit node capacitance loading and, hence, the circuit speed. As design rules are reduced to about 0.12 micron and below, the rejection rate due to integrated circuit speed delays significantly reduces production throughput and increases manufacturing costs. Moreover, as line widths decrease electrical conductivity and electromigration resistance become increasingly important.
Cu and Cu alloys have received considerable attention as a candidate for replacing Al in interconnect metallizations. Cu is relatively inexpensive, easy to process, and has a lower resistively than Al. In addition, Cu has improved electrical properties vis-a-vis W, making Cu a desirable metal for use as a conductive plug as well as conductive wiring.
An approach to forming Cu plugs and wiring comprises the use of damascene structures employing CMP. However, due to Cu diffusion through interdielectric layer materials, such as silicon dioxide, Cu interconnect structures must be encapsulated by a diffusion barrier layer. Typical diffusion barrier metals include tantalum (Ta), tantalum nitride (TaN), titanium nitride (TiN), titanium (Ti), titanium-tungsten (TiW), tungsten (W), tungsten nitride (WN), Ti-TiN, titanium silicon nitride (TiSiN), tungsten silicon nitride (WSiN), tantalum silicon nitride (TaSiN) and silicon nitride for encapsulating Cu. The use of such barrier materials to encapsulate Cu is not limited to the interface between Cu and the dielectric interlayer, but includes interfaces with other metals as well.
In implementing Cu metallization, particularly in damascene techniques wherein an opening is formed in a dielectric layer, particularly a dielectric layer having a low dielectric constant, e.g., a dielectric constant less than about 3.9, various reliability, electromigration and resistance issues are generated. Reliability issues stem, in part, from the difficulty in forming a continuous seedlayer on a barrier layer in an opening, particularly as the feature sizes continue to shrink into the deep submicron regime. For example, an opening is formed in dielectric layer 10, as illustrated in FIG. 1. A seedlayer for deposition of Cu 12 is then deposited by physical vapor deposition (PVD). As a result of reduced feature sizes and high aspect ratios, it is extremely difficult to deposit a continuous seedlayer lining the opening. Consequently, discontinuities in seedlayer 12 form, as illustrated by reference numeral 13. In addition, it is even difficult to effectively plate the seedlayer 12 on the bottom of the opening. Cu cannot be electroplated on a discontinuous seedlayer or where no seedlayer exists. Consequently, voids are induced leading to high resistance vias and lines or opening circuits.
Accordingly, there exists a need for methodology enabling the formation of reliable Cu interconnects with reduced resistivity and reduced voids.
An advantage of the present invention is a method of manufacturing a semiconductor device having reliable, low resistance Cu or Cu alloy interconnects with significantly reduced voids.
Additional advantages and other features of the present invention will be set forth in the description which follows and, in part, will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present invention. The advantages of the present invention may be realized and obtained as particularly pointed out in the appended claims.
According to the present invention, the foregoing and other advantages are achieved in part by a method of manufacturing a semiconductor device, the method comprising: forming an opening in a dielectric layer; depositing a barrier layer lining the opening; depositing a seedlayer for copper (Cu) or Cu alloy deposition on the barrier layer; depositing a seedlayer enhancement film by chemical vapor deposition on the seedlayer; laser thermal annealing the seedlayer enhancement film; and filling the opening with Cu or a Cu alloy.
Embodiments include forming a dual damascene opening in dielectric material having a dielectric constant no greater than about 3.9, such as a fluorine (F)-containing oxides, such as an F-containing oxide derived from tetraethyl orthosilicate (TEOS), the opening comprising an upper trench section in communication with a lower via hole section; depositing a composite barrier layer lining the opening, the composite barrier layer comprising a layer of tantalum nitride and a layer of xcex1-tantalum thereon; depositing a seedlayer by PVD on the xcex1-tantalum layer, the deposited seedlayer having discontinuities, depositing a conformal seedlayer enhancement film by chemical vapor deposition bridging discontinuities in the seedlayer and having a rough surface; laser thermal annealing the seedlayer enhancement film in flowing nitrogen to reduce the roughness of the seedlayer enhancement film; and filling the opening with Cu or a Cu alloy to form a Cu or Cu alloy line in communication with an underlying Cu or Cu alloy via. Embodiments of the present invention include laser thermal annealing by impinging a pulsed laser light beam on the rough exterior surface of the deposited seedlayer enhancement film at a radiant fluence of about 0.084 to about 0.136 joules/cm2 for about 10 to about 100 nanoseconds, thereby elevating the temperature of the seedlayer enhancement film to about 300xc2x0 C. to about 500xc2x0 C.